linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
* [PATCH] x86, apic: Handle a bad TSC more gracefully
@ 2014-10-15 17:12 Andy Lutomirski
  2014-10-22 19:34 ` [tip:x86/urgent] " tip-bot for Andy Lutomirski
  0 siblings, 1 reply; 2+ messages in thread
From: Andy Lutomirski @ 2014-10-15 17:12 UTC (permalink / raw)
  To: x86, linux-kernel, Thomas Gleixner; +Cc: Bandan Das, Andy Lutomirski, stable

If the TSC is unusable or disabled, then this patch fixes:

 - Confusion while trying to clear old APIC interrupts.
 - Division by zero and incorrect programming of the TSC deadline
   timer.

This fixes boot if the CPU has a TSC deadline timer but a missing or
broken TSC.  The failure to boot can be observed with qemu using
-cpu qemu64,-tsc,+tsc-deadline

This also happens to me in nested KVM for unknown reasons.
With this patch, I can boot cleanly (although without a TSC).

Cc: stable@vger.kernel.org
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
---
 arch/x86/kernel/apic/apic.c | 4 ++--
 arch/x86/kernel/tsc.c       | 5 ++++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 67760275544b..24b5894396a0 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1297,7 +1297,7 @@ void setup_local_APIC(void)
 	unsigned int value, queued;
 	int i, j, acked = 0;
 	unsigned long long tsc = 0, ntsc;
-	long long max_loops = cpu_khz;
+	long long max_loops = cpu_khz ? cpu_khz : 1000000;
 
 	if (cpu_has_tsc)
 		rdtscll(tsc);
@@ -1383,7 +1383,7 @@ void setup_local_APIC(void)
 			break;
 		}
 		if (queued) {
-			if (cpu_has_tsc) {
+			if (cpu_has_tsc && cpu_khz) {
 				rdtscll(ntsc);
 				max_loops = (cpu_khz << 10) - (ntsc - tsc);
 			} else
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index b6025f9e36c6..b7e50bba3bbb 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1166,14 +1166,17 @@ void __init tsc_init(void)
 
 	x86_init.timers.tsc_pre_init();
 
-	if (!cpu_has_tsc)
+	if (!cpu_has_tsc) {
+		setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
 		return;
+	}
 
 	tsc_khz = x86_platform.calibrate_tsc();
 	cpu_khz = tsc_khz;
 
 	if (!tsc_khz) {
 		mark_tsc_unstable("could not calculate TSC khz");
+		setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
 		return;
 	}
 
-- 
1.9.3


^ permalink raw reply related	[flat|nested] 2+ messages in thread
* [tip:x86/urgent] x86, apic: Handle a bad TSC more gracefully
  2014-10-15 17:12 [PATCH] x86, apic: Handle a bad TSC more gracefully Andy Lutomirski
@ 2014-10-22 19:34 ` tip-bot for Andy Lutomirski
  0 siblings, 0 replies; 2+ messages in thread
From: tip-bot for Andy Lutomirski @ 2014-10-22 19:34 UTC (permalink / raw)
  To: linux-tip-commits; +Cc: luto, linux-kernel, bsd, mingo, tglx, hpa

Commit-ID:  b47dcbdc5161d3d5756f430191e2840d9b855492
Gitweb:     http://git.kernel.org/tip/b47dcbdc5161d3d5756f430191e2840d9b855492
Author:     Andy Lutomirski <luto@amacapital.net>
AuthorDate: Wed, 15 Oct 2014 10:12:07 -0700
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Wed, 22 Oct 2014 21:31:46 +0200

x86, apic: Handle a bad TSC more gracefully

If the TSC is unusable or disabled, then this patch fixes:

 - Confusion while trying to clear old APIC interrupts.
 - Division by zero and incorrect programming of the TSC deadline
   timer.

This fixes boot if the CPU has a TSC deadline timer but a missing or
broken TSC.  The failure to boot can be observed with qemu using
-cpu qemu64,-tsc,+tsc-deadline

This also happens to me in nested KVM for unknown reasons.
With this patch, I can boot cleanly (although without a TSC).

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Bandan Das <bsd@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/e2fa274e498c33988efac0ba8b7e3120f7f92d78.1413393027.git.luto@amacapital.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/x86/kernel/apic/apic.c | 4 ++--
 arch/x86/kernel/tsc.c       | 5 ++++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 6776027..24b5894 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -1297,7 +1297,7 @@ void setup_local_APIC(void)
 	unsigned int value, queued;
 	int i, j, acked = 0;
 	unsigned long long tsc = 0, ntsc;
-	long long max_loops = cpu_khz;
+	long long max_loops = cpu_khz ? cpu_khz : 1000000;
 
 	if (cpu_has_tsc)
 		rdtscll(tsc);
@@ -1383,7 +1383,7 @@ void setup_local_APIC(void)
 			break;
 		}
 		if (queued) {
-			if (cpu_has_tsc) {
+			if (cpu_has_tsc && cpu_khz) {
 				rdtscll(ntsc);
 				max_loops = (cpu_khz << 10) - (ntsc - tsc);
 			} else
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index b6025f9..b7e50bb 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1166,14 +1166,17 @@ void __init tsc_init(void)
 
 	x86_init.timers.tsc_pre_init();
 
-	if (!cpu_has_tsc)
+	if (!cpu_has_tsc) {
+		setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
 		return;
+	}
 
 	tsc_khz = x86_platform.calibrate_tsc();
 	cpu_khz = tsc_khz;
 
 	if (!tsc_khz) {
 		mark_tsc_unstable("could not calculate TSC khz");
+		setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
 		return;
 	}
 

^ permalink raw reply related	[flat|nested] 2+ messages in thread
end of thread, other threads:[~2014-10-22 19:34 UTC | newest]

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-10-15 17:12 [PATCH] x86, apic: Handle a bad TSC more gracefully Andy Lutomirski
2014-10-22 19:34 ` [tip:x86/urgent] " tip-bot for Andy Lutomirski

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).